Free Health & Fitness Calculators
Body composition, energy needs, training zones and pacing — each explaining which formula it uses and where that formula stops being reliable.
58 free tools · no signup
A1C Calculator
Convert A1C percentage to estimated average glucose (eAG) or the reverse, in mg/dL and mmol/L.
Alcohol Units Calculator
Convert drink volume and ABV into US standard drinks, UK units, and pure alcohol grams.
BAC Calculator
Estimate blood alcohol content from drinks, weight and time using the Widmark formula.
BMR Calculator
Calculate your Basal Metabolic Rate using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.
Baby Percentile Calculator
Estimate your baby's weight and height percentile from simplified growth-chart bands.
Blood Pressure Calculator
Enter your systolic and diastolic numbers to see your ACC/AHA blood pressure category instantly.
Blood Sugar Converter
Convert blood glucose between mg/dL and mmol/L with target-range context.
Body Fat Calculator
Estimate body fat percentage with the proven U.S. Navy tape-measurement method — free.
Body Recomposition Calculator
Get target weight, calories, and protein for losing fat while preserving muscle.
Body Surface Area Calculator
Estimate your BSA in m² using Du Bois, Mosteller, and Haycock clinical formulas.
Caffeine Calculator
Add up your coffee, tea, and energy drinks to see total daily caffeine vs. the 400mg limit.
Calorie Deficit Calculator
Turn your weight-loss goal and timeframe into a safe daily calorie target.
Calories Burned Calculator
Estimate calories burned for 20+ activities using MET values and your body weight.
Child Height Predictor
Predict your child's adult height range using mom and dad's height (mid-parental method).
Conception Date Calculator
Estimate your baby's conception date from a due date, birth date, or last period.
Cycling Calorie Calculator
Estimate calories burned cycling from your weight, duration, and intensity.
FFMI Calculator
Calculate your Fat-Free Mass Index and see how it compares to the natural muscle ceiling.
Fasting Timer
Track an active fast: elapsed time, remaining time, end time, and metabolic stage.
Fertility Calculator
Find your fertile window and best days to try to conceive this cycle.
Heart Rate Zone Calculator
See all 5 heart rate training zones from recovery to max effort in one view.
Ideal Weight Calculator
Compare Devine, Robinson, Miller, and Hamwi formulas to find your healthy weight range.
Intermittent Fasting Calculator
Build your exact eating and fasting window for 16:8, 18:6, 20:4, OMAD, or 5:2.
Keto Calculator
Get your daily calories plus a fat, protein, and net-carb split built for a ketogenic diet.
Lean Body Mass Calculator
Find your lean body mass, fat mass, and body fat percentage using the Boer formula.
Macro Calculator
Get your daily calorie, protein, carb, and fat targets based on your body stats and goal.
Maintenance Calorie Calculator
Find the exact calories that keep your weight flat, using BMR and activity level.
Marathon Time Predictor
Predict your marathon finish time from a recent 5K, 10K, or half marathon using Riegel's formula.
Max Heart Rate Calculator
Estimate your max heart rate with three formulas plus your 50-85% training range.
Menopause Calculator
Estimate your likely perimenopause window and menopause age from age, family history, and smoking.
One Rep Max Calculator
Estimate your one-rep max from any set using Epley, Brzycki, or Lombardi formulas.
Ovulation Calculator
Estimate your ovulation date, fertile window, and most fertile days from your last period.
Pace Converter
Convert running pace between min/mile, min/km, mph, and km/h instantly.
Period Calculator
Predict your next period, cycle day, and fertile window from your last period date.
Pregnancy Due Date Calculator
Estimate your due date, current week, trimester, and conception date instantly.
Pregnancy Week Calculator
Find out exactly how many weeks and days pregnant you are, your trimester, and your due date.
Running Calorie Calculator
Estimate calories burned running from your weight, distance, and pace.
Running Pace Calculator
Free pace calculator — pace per km/mile and speed for any distance and time.
Sleep Cycle Calculator
Find the ideal bedtime or wake time based on 90-minute sleep cycles so you wake up refreshed.
Sleep Time Calculator
See how much sleep is recommended for your age and compare it to your actual sleep and weekly debt.
Smoking Cost Calculator
Calculate the true daily, monthly, and lifetime cost of smoking — plus what you'd have if you invested it instead.
Sobriety Calculator
Count your days sober, hit milestones, and see the money you've saved.
Steps to Calories Calculator
Convert your daily steps into estimated calories burned, distance, and per-1,000-step rate.
Steps to Miles Calculator
Convert your step count into accurate miles and km using your real height-based stride.
Sugar Intake Calculator
Add up your daily added sugar and compare it to the AHA and WHO recommended limits.
Swimming Calorie Calculator
Estimate calories burned swimming based on your weight, duration, and stroke or intensity level.
TDEE Calculator
Find how many calories your body burns daily and how many to eat for your goal — free.
Target Heart Rate Calculator
Get a personalized target heart rate using the Karvonen heart-rate reserve method.
Treadmill Pace Calculator
Convert treadmill mph/km-h and incline into pace and outdoor-equivalent effort.
VO2 Max Calculator
Estimate your VO2 max using resting HR, 1.5-mile run, Cooper, or Rockport walk tests.
Waist to Height Ratio Calculator
Find your waist-to-height ratio and see if your waist is under half your height.
Waist to Hip Ratio Calculator
Get your WHR, WHO risk category, and apple vs. pear body shape from waist and hip measurements.
Walking Calorie Calculator
See how many calories you burn walking, by distance, time, pace and body weight.
Water Intake Calculator
Personalised daily water intake calculator by weight, activity and climate.
Water Weight Calculator
Estimate your total body water in liters and see why daily scale swings are usually water, not fat.
Weight Loss Calculator
Project the weeks and date you'll reach your goal weight at your current pace.
Weight Loss Percentage Calculator
Find the percentage of body weight you've lost and your progress toward goal.
Wilks Calculator
Calculate your Wilks score to compare powerlifting strength fairly across bodyweights.
⚖️ BMI Calculator
Find your Body Mass Index and see which weight category you fall into — free and private.
Every formula is named
There is no single correct way to estimate body fat, resting metabolism or maximum heart rate; there are several published equations that disagree with each other. These tools state which one they use — Mifflin-St Jeor, US Navy circumference, Karvonen — because a number without its method cannot be compared with a number from anywhere else.
Where the estimates break down
BMI does not distinguish muscle from fat and was never designed to assess an individual. Predictive maximum-heart-rate formulas carry a standard deviation of roughly ten beats per minute. Calorie estimates assume an average that describes very few actual people. Each page says so, because a tool that presents an estimate as a measurement is misleading regardless of how well it calculates.
Information, not advice
These pages explain how a calculation works and what its output means. None of them tells you what to eat, how to train, or whether a result is a problem — those are questions for a qualified professional who can see your full picture. Every page in this set carries that statement explicitly.
